1. Technical Field
This invention pertains to engine nozzles in general, and to seals for sealing between flaps within the engine nozzle in particular.
2. Background Information
In certain gas turbine driven aircraft, it is advantageous to equip the engine with a convergent-divergent (c/d) exhaust nozzle. The term "convergent-divergent" describes an exhaust nozzle having a convergent section upstream of a divergent section. Exhaust gases exiting the turbine phase of the engine pass through the decreasing diameter convergent section before passing through the increasing diameter divergent section.
In engines having conventional c/d nozzles, both the convergent and divergent sections are symmetric about the longitudinal axis of the engine. The divergent section includes a plurality of flaps, hinged at the interface between the convergent and divergent sections, which can be pivoted radially outward to increase the angle at which the divergent section diverges from the longitudinal axis. Flap seals are positioned between the flaps of the divergent section to prevent exhaust gas from escaping between the flaps.
In gas turbine engines featuring vectorable c/d exhaust nozzles, the centerline of the divergent section may be skewed from the longitudinal centerline to create pitch and yaw thrust vectoring. Skewing the divergent flaps causes the position of the flaps relative to one another to vary depending upon the direction and magnitude of the skew and the position of the particular flap relative to the skew. In some areas, the spacing between flaps decreases. In other areas, the spacing between flaps increases and assumes a more complicated geometry. In addition, skewing the flaps and flap seals into the flow path of the exhaust gas causes the mechanical and thermal load on the flaps and flap seals to increase.
Hence, what is needed is an exhaust nozzle flap seal that can accommodate complex geometries and can accommodate increased mechanical and thermal loads.